Tumor separation surgery followed by high-dose hypofractionated stereotactic radiosurgery (SRS) or high-dose single-fraction SRS is safe and effective in controlling spinal metastases regardless of the radiosensitivity of the particular tumor type that has invaded the spine.
Treatment of metastatic spine tumors “is palliative with the goal of improving or maintaining neurologic function, achieving spine stability, relieving pain, and providing durable tumor control,” explained the authors of this study, which was published in the Journal of Neurosurgery: Spine (2013; doi:10.3171/2012.11.SPINE12111). The object is to make the patient as comfortable and neurologically functional as long as possible despite the presence of systemic disease. In this situation sometimes less surgery is better.
Unlike conventional external beam radiation therapy, SRS delivers a far more focused beam of radiation to the tumor. This allows physicians to deliver large doses of radiation to diseased portions of the body and still protect surrounding healthy tissue from the radiation’s effects. The authors point out that radiosensitive tumors can be treated successfully with lower doses of radiation delivered by conventional external beam radiation therapy; radioresistant tumors, on the other hand, require large doses of radiation, which are best delivered by SRS. By first performing separation surgery, creating a space between the spine and the remaining tumor, the surgeons protect the spinal cord from the high levels of radiation needed to treat radioresistant tumors.
The researchers, affiliated with Memorial Sloan-Kettering Cancer Center in New York, New York, reviewed and analyzed data in the charts of 186 patients who presented with epidural spinal cord compression due to spinal metastases. All of these patients underwent tumor separation surgery to decompress the spinal cord and stabilize the spine sometime between 2002 and 2011. During this procedure the tumor was dissected away from the spinal cord—or separated—providing a space between the spinal dura and any remaining tumor. Unlike in traditional spinal tumor surgery, extensive tumor resection was not pursued to reduce surgical morbidity. The spine was also stabilized with screws and rods.
Within 2 to 4 weeks after surgery, SRS was performed to deliver radiation to the remaining metastatic tumor without damaging the spinal cord. In 40 patients (21.5%), radiation was delivered in a single 24-Gray (Gy) dose to the tumor (high-dose single-fraction SRS). In 37 patients (19.9%), a median total dose of 27 Gy (range 24 to 30 Gy) was delivered in three fractions (high-dose hypofractionated SRS), and in 109 patients (58.6%) a median total dose of 30 Gy (range 18 to 36 Gy) was delivered in five or six fractions (low-dose hypofractionated SRS).
Better tumor control was found in the patients who underwent high-dose hypofractionated SRS than in those who underwent low-dose hypofractionated SRS, with 1-year cumulative local progression rates of 4.1% in the high-dose group and 22.6% in the low-dose group, which was a statistically significant difference. The 1-year cumulative local progression rate was 9.0% for the patients who underwent single-fraction SRS.